Process of preparing sulphonium compounds



Patented Apr. 13, 1943 PROCESS OF PREPAR ING SULPHONIUM OUNDS Arthur E. Bearse, Grandview Heights, 'and Richard S. signors to Shutt, Upper Arlington, Ohio, as- Battelle Memorial Institute, 00-

lumbus, Ohio, a corporation of Ohio No Drawing. Application May 16, 1940,

Serial No. 335,548

4 Claims.

This invention relates to a process of preparing sulphonium compounds without the use of expensive reagents and more particularly relates to a process of hydrolyzing sulphonium alkyl sulphates in the presence of acidic substances and converting the sulphonium sulphates thus formed. into sulphonium bases and salts.

It is known that organic sulphides and alkyl halides interact to form sulphonium halides. These sulphonium halides can be reacted with moist silver oxide to form sulphonium bases.

This method of preparing sulphonium bases is expensive in that it involves the use of costly silver oxide and, in many instances, requires the use of alkyl iodides instead of the less reactive and less costly alkyl bromides and chlorides.

While it is known that certain organic sulphides will react with methyl or ethyl sulphate to form sulphonium alkyl sulphates, it does not appear that any satisfactory method of converting these alkyl sulphates into sulphonium bases has been discovered.

It is, therefore, an object of this invention to provide an inexpensive, easily conducted process of preparing sulphonium bases.

Another object of the invention is to provide a method of preparing sulphonium bases from sulphonium alkyl sulphates.

A further object of the invention is to provide a simple method of obtaining sulphonium salts.

A specific object of the invention is to provide a method of converting sulphoniumalkyl sulphates into sulphonium sulphates in the presence of acidic substances.

, A specific object of the invention is to convert sulphonium sulphates into sulphonium bases bythe use of stronginorganic bases which formsulphates of low solubility in water.

According to this invention sulphonium alkyl sulphates are hydrolyzed in .the presence of acidic substances such as, for example, sulphuric acid, phosphoric acid, oxalic acid, citric acid and the like. sulphonium salts are formed by this hydrolysis and these salts can be reacted with suitable inorganic salts or bases to yield other sulphonium salts or sulphonium bases.

In a more limited sense the invention pertains to the hydrolysis of sulphonium alkyl sulphates to sulphonium sulphates in the presence of acids which are capable of forming metal salts of low solubility in water. Sulphuric acid is a preferred hydrolyzing catalyst and barium hydroxide is a preferred converting agent for reacting with the sulphuric acid and with the sulphonium sulypaate after hydrolysis is complete to produce insoluble tiii R: [R ]S04+2R|0H+H:SO|,

R R1 R1 [Rz SlSOH-Ba(0fi)1 2 R, s--0H+Baso R2 2 Rs i In the above formulae R1 and R4 represent alkyl groups, while'Rz and R3 represent saturated or unsaturated hydrocarbon radicals which may contain other substituents. In some in-, stances R2 and R3 may form a saturated heterocyclic structure with the sulphur. The invention will be more fully understood from the following detailed examples in which the parts given are parts by weight unless otherwise specified. It should be understood that these examples merely illustrate preferred embodiments of the invention and do not limit the scope of the invention.

Example I 188 parts of trimethyl sulphonium methyl sulphate, prepared as described hereinbelow, are dissolved in 800 parts of 12% sulphuric acid. The solution is refluxed for about 6 hours. The refluxed solution is then neutralized with barium hydroxide to produce a solution of trimethyl sulphonium sulphate and a precipitate of barium sulphate. The solution is filtered free from the barium sulphate and reacted with the required additional amount of barium hydroxide at to C. to produce a solution of trimethyl sulphonium hydroxide. The additionally formed barium sulphate can be removed by filtration.

The strongly basic solution or trimethyl sulphonium hydroxide can be concentrated by evaporation under reduced pressure.

If desired, the neutral solution of trimethyl sulphonium sulphate obtained as described above.

can be treated with thenecessary quantity of barium chloride followed by filtration from bariuin chloride followed by filtration from barium sulphate to produce a solution of trimethyl sulphonium chloride instead of the base.

The tr 'l ihcnium methyl sulphate is by parts of dimethyl sulphate during a one-half hour period to 62 parts of dimethyl sulphide while stirring the mixture in a reaction vessel provided with a reflux condenser. The trimethyl sulphonium methyl sulphate is obtained as a crystalline, hygroscopic material which is very soluble in water.

Example II 244 parts of triethyl sulphonium ethyl sulphate, prepared as described hereinbelow, are dissolved in 800 parts of 12% sulphuric acid and the solution is boiled under refl'ux for about 6 hours. The acid solution of triethyl sulphonium sulphate thus formed is neutralized by the addition of barium hydroxide. The neutral solution of triethyl sulphonium sulphate is reacted with the required additional amount of barium hydroxide to produce a solution of triethyl sulphonium hydroxide in good overall yield. The solution is filtered free from barium sulphate and may be concentrated by evaporation under reduced pressure.

If the neutral solution of triethyl sulphonium sulphate, prepared as described above, is treated with the necessary quantity of barium nitrate followed by a filtration from barium sulphate, a solution of triethyl sulphonium nitrate is prepared instead of the base.

The triethyl sulphonium ethyl'sulphate used as a starting material in this example, can be obtained in excellent yield by heating 90 parts of diethyl sulphide with 154 parts of diethyl sulphate under reflux ona steam bath for one hour. The compound is a viscous liquid, very soluble in water, but insoluble in ether or benzene.

Example III 216 parts of dimethyl ethyl sulphonium ethyl sulphate are used in place of triethyl sulphonium ethyl sulphate as in Example 11, and the same steps as described in Example II are carried out to produce a good yield of dimethyl ethyl sulphonium hydroxide.

The dimethyl ethyl sulphonium ethyl sulphate is prepared by heating a mixture of 62 parts of dimethyl sulphide and 154 parts of diethyl sulphate for 4 hours on a steam bath in a reaction vessel provided with a reflux condenser and a mechanical stirrer. The viscous sulphonium salt is very soluble in water but insoluble in ether.

Example IV 272 parts of diethyl n-propyl sulphonium npropyl sulphate, made as described below, are dissolved in 800 parts of 12% sulphuric acid, and the solution is refluxed for 6 to 8 hours. After cooling to 50 C., a hot aqueous solution of barium hydroxide is slowly added with stirring until a filtered test portion no longer shows an excess of sulphate ion when treated with barium chloride solution. The barium sulphate is re- Example V A solution of 30') parts of diethyln-butyl sulphonium n-butyl sulphate in 800 parts of 12% sulphuric acid is refluxed for 6 to 8 hours. After cooling to about C., a hot aqueous solution 'of barium hydroxide is added gradually in sumcient quantity to precipitate substantially all of the sulphate ions as barium sulphate. Filtration from barium sulphate leaves a strongly basic solution of diethyl n-butyl sulphonium hydroxide.

,Diethyl n-butyl sulphonium n-butyl sulphate is made as follows:--A mixture of 90 parts of diethyl sulphide and 210 parts of di-n-butyl sulphate was placed in a vessel fitted with a mechanical stirrer, reflux condenser and thermometer. The temperature was raised during 15 minutes to 130 C. and held at 130-140" C. during 45 minutes. The sulphonium compound thus obtained was purified by dissolving in acetone, precipitating with ether, and drying in a vacuum over a suitable desiccant.

Example VI low, in 800 parts of 12% sulphuric acid is refluxed for 8 hours. When the solution has cooled,

it is treated with barium hydroxide as required to neutralize the acid and to convert the sulphonium sulphate into diallyl methyl sulphonium hydroxide. The barium sulphate is removed by filtration and some water insoluble material resulting from decomposition of the base is taken up in ether. The yield of sulphonium base is reduced by the decomposition.

Diallyl methyl sulphonium methyl sulphate is prepared by heating 114 parts of diallyl sulphide to 90-95 C. on a steam bath and adding during 10 minutes 126 parts of dimethyl sulphate with stirring. Heating on the steam bath and stirring are continued for one-half hour. The material may be purified by dissolving in acetone, precipitating with ether, and drying over a desiccant in a vacuum. A good yield of diallyl methyl sulphonium methyl sulphate is obtained.

moved by filtration and washed with water. The

filtrate consists of an aqueous solution of diethyl 'n-propyl sulphonium hydroxide, which may be concentrated by evaporation under reduced pressure.

The diethyl n-propyl sulphonium n-propyl sulphate required for' the above may be prepared by heating for 1 hour at l30140 C. under a reflux condenser a stirred mixture of 90 parts of ethyl sulphide and 182 parts of n-propyl sulphate. The product may be purified by dissolving in acetone, precipitating with ether, and drying in a vacuum over a suitable desiccant. The sulphonium salt is very soluble in water.

Example VIII A solution of 306 parts of benzyl diethyl sulphonium ethyl sulphate (see below) in 800 parts tration from barium sulphate leaves a solution of benzyl diethyl sulphonium hydroxide.

Benzyl diethyl sulphonium ethyl sulphate isitself obtained by heating with stirring a mixture of equimolecular portions of benzyl ethyl sulphide and ethyl-sulphate for 1 hour at 130140 C. The sulphonium salt is a viscous liquid, soluble in water.

Example X 188 parts of trimethyl sulphonium methyl sulphate, prepared as described in Example I, are dissolved in 800 parts of dilute hydrobromic acid containing 80.9 parts of hydrogen bromide. The solution is refluxed for 8 to 10 hours. By addition of barium hydroxide to the solution until no longer acid, filtration from barium sulphate, and evaporation of the solvent, trimethyl sulphonium bromide is obtained as a white, crystalline solid.

From the above examples it should be understood that the sulphonium alkyl sulphates required for the present invention may be readily prepared by the interaction of an organic sulphide and an alkyl sulphate; The term organic sulphide is intended to cover any compound in which sulphur is linked directly to two hydrocarbon radicals, or in which. sulphur is attached directly to two carbon atoms as part of a saturated heterocyclic ring. The organic sulphide may contain more than one sulphur atom thus linked. The sulphides may contain substituents of any kind provided that such groups do not have a deleterious effect on the reaction. Suitable substitutents are, for example, alkoxyl, carsulphide, di-n-butyl sulphide, ,methyl dodecyl sulphide, ethyl isopropyl sulphide, methyl tertiarybutyl sulphide, diallyl sulphide, benzyl ethyl sulphide, dibenzyl sulphide, pheny ethyl sulphide, diphenyl sulphide, tetramethylene sulphide, di- (beta-hydroxyethyl) sulphide, and the dimethylthioether of ethylene dimercaptan.

Alkyl sulphates which may be reacted with the organic sulphides to form sulphonium alkyl sulphates are, for example, dimethyl sulphate, methyl ethyl sulphate, diethyl sulphate, di-npropyi sulphate, di-n-butyl' sulphate, and the like While most of the above examples refer to the use of sulphuric acid as a catalyst for the hydrolysis of the sulphonium alkyl sulphate it should be understood that the hydrolysis is catalyzed by hydrogen ions and that these can arise from any acidic material with the exception of substances, such as chromic acid, which exert an oxidizing action on the organic material. The important feature oi thisphase of the present invention is that the hydrolysis is carried out in a medium having a pH value numerically less than 7. The use of another acidic agent than sulphuric acid, namely, hydrobromic acid, is illustrated by Example X. The sulphuric acid is particularly suitable as a catalyst because of its low cost and because it can be subsequently removed as barium sulphate after neutralization with barium hydroxide.

Phosphoric acid, oxalic acid, citric acid, and the like acidic materials are suitable substitutes for sulphuric acid. Alkyl sulphuric acids can also be used since they themselves are hydrolyzed to sulphuric'acidand an alcohol under the re acting conditions. The concentration of the acids can be widely varied, although when only dilute acids are used as the hydrolyzing medium,

the rate of hydrolysis of the sulphonium alkyl sulphate may be too slow for practical purposes.

The hydrolysis of sulphonium alkyl sulphates may be carried out at the boiling point of the solutions as described in the examples presented above, or more slowly at lower temperatures. It is also possible to conduct the hydrolysis at higher temperatures under superatmospheric pressure, provided thatthe sulphonium salts are suifioiently stable, in order to increase the rate of hydrolysis. In this connection it should he noted that gases such as carbon dioxide, which have an acid reaction in water, can be used under pressure as a means of securing an acid medium for the hydrolysis of the sulphonium alkyl sul phates. The neutralization of the sulphuric acid present in the solution subsequent to the hydrolysis is best accomplished by the use of an oxide, hy=- droxide, carbonate or basic carbonate of those metals which form sulphates of low solubility in water such as barium, calcium, strontium, and lead. The fact that sulphuric acid is always formed as one product of the hydrolysis, regardless of the catalyst selected, limits the choice of neutralizing agent to one including a basic metal compound having the above mentioned property. The preferred reagent for conversion of the sulphonium sulphates to sulphonium bases is barium hydroxide, although strontium hydroxide is quite suitable. Calcium hydroxide is unsatisfactory because of the close similarity in water Eli solubility between calcium hydroxide and calcium sulphate. If, as in Example I above, it is desired to prepare another sulphonium salt, in- I stead of the base, from a sulphonium sulphate, it is possible to use a soluble salt of any metal which forms a relatively insoluble sulphate; In the example cited, barium chloride is used to, obtain a solution of trimethyl sulphonium chloride. In a similar manner calcium or strontium chloride, and the bromides, iodides, nitrates, acetates, and the like of barium, calcium and strontium may be used to obtain the corresponding sulphonium salt and an insoluble sulphate which may be removed by filtration.

An alternative method of obtaining sulphonium salts is to carry out the hydrolysis of the sulphonium alkyl sulphate in the presence of an equivalent quantity of the acid corresponding to the salt desired, as in Example X above. The sulphuric acid resulting from the hydrolysis can then be removed as barium sulphate after neutralization with barium hydroxide, leaving an aqueous solution of the sulphonium salt.

This invention provides a simple, inexpensive, andconvenlent method for the preparation of sulphonium bases and salts. Certain of these compounds have been described as being useful as carbon removers, in the manufacture of textiles, as waterproofing agents for leather, as sur face-active agents, as addition agents for dry cleaning fluids, and as disinfectants.

If an acid other than sulphuric acid is used, to effect hydrolysis of the sulphonium alkyl Sill phates, the sulphuric acid liberated. during the hydrolysis may be neutralized with a barium, strontium, calcium, lead or equivalent compoundv While the hydrolyaing acid is neutraiized with a metallic compound forming an insoluble compound therewith; For instance, when oxalic acid is used, calcium hydroxide may be added to remove the oxalic acid as calcium oxalate.

It will, of course, be understood that various details of the process may be varied through a wide range without departing from the principles of this invention and it is therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

We claim as our invention:

1. The process of preparing a sulphonium compound which includes heating a sulphonium alkyl sulphate in an aqueous medium containing an appreciable amount of acid and devoid of precipitants of the sulphonium alkyl sulphate, said heating being continued for a time sufflcient to hydrolyze said sulphonium alkyl sulphate.

2. The process of preparing a sulphonium base which includes heating a sulphonium alkyl sulphate in an aqueous medium devoid of precipitants of the sulphonium alkyl sulphate and containing an appreciable amount of acid, said heating being continued for a time suflicient to hydrolyze said sulphonium alkyl sulphate whereby a sulphonium salt, alkyl alcohol and sulphuric acid are formed, and thereafter precipitating said acid and said sulphuric acid with basic material containing cations forming insoluble compounds.

with said acid and said sulphuric acid whereby said sulphonium salt is transformed into a sul-. phonium base.

3. The method of preparing a sulphonium base which includes heating a sulphonium alkyl sulphate in an aqueous medium devoid of precipitants for'said sulphonium alkyl sulphate and. containing an appreciable amount of sulphuric acid, said heating being continued for a time suflicient to hydrolyze said sulphonium alkyl sulphate whereby a sulphonium sulphate, alkyl alcohol and sulphuric acid are formed, and thereafter precipitating, all sulphate ions present in the products of said hydrolysis with barium hydroxide whereby said sulphonium sulphate is transformed intoa sulphonium base.

4. The method of preparing a sulphonium halide which includes heating a sulphonium alkvl sulphate in an aqueous medium devoid of precipitants for said sulphonium alkyl sulphate and containing an appreciable amount of sulphuric acid, said heating being continued for a time suflicient to hydrolyze said sulphonium alkyl sulphate whereby a sulphonium sulphate, alky] alcohol and sulphuric acidare formed, and thereafter precipitating all sulphate ions present in the products of said hydrolysis with a barium halide whereby said sulphonium sulphate is transformed into a sulphonium halide.

ARTHUR E. BEARSE. RICHARD S. SHUTT. 

